Field of the Invention
This invention relates to modular photovoltaic systems.
Background of the Invention
Solar power systems are typically mounted in a location facing the sun in order to maximize the exposure to solar energy. However, there can be obstructions to the direct sunlight needed to power the solar panels. Clouds, trees, and architectural features or building elements can cause shading. Even partial shading of the solar panel can dramatically reduce the power output since the electron flow inside the panel is in series. Shading of only one section or portion of the solar panel will block the flow for the entire panel or group of panels.
Traditional solar power systems normally include multiple solar panels that are connected to each other by either parallel or series wiring (or a combination of both).
Prior to the introduction of microinverters, most if not all solar power systems were wired in series, having several “strings” of panels (a group of many panels, circuited in series), with each string feeding into a large power inverter that converted the DC power to AC power. The main disadvantage of this design is the fact that if there is shading on even one single panel within the string, it affects the current flow of that entire string (because they are wired in series), and reduces the total string power output to the lowest electrical current flow restriction created by the shading of that one panel.
By wiring the system in a parallel configuration, this problem can be solved. The parallel wired systems typically invert the DC power to AC at each individual solar panel via a microinverter. This parallel wired microinverter configuration allows each individual solar panel to operate independently, and contribute its portion of power production to the overall power of the combined system without restricting the current flow. If there is shading on one single panel, the lower power production of that panel does not restrict the total power production of the parallel string.
Many approaches to making solar power systems “modular” or easily expandable have been proposed in order to simplify the installation of the system. A large portion of these consist of unique mounting systems that attach to the roof, and connection techniques that allow multiple solar modules or panels to be connected together. The attachment system usually has some kind of rack or structure that first attaches to the roof or building structure, then the solar panels are mechanically attached to that support structure.
Some of the proposed modular systems incorporate parallel wiring along with microinverters that parallel with each other in order to interface with an AC system connected to the utility. However, they convert it to AC before performing the paralleling function. The parallel wiring is not typically incorporated within each individual module. The parallel wiring that connects multiple solar modules is normally run separate from the module in a protected cabling, raceway or electrical bus structure. Also, the electronics that perform the paralleling function are typically in a separate enclosure such as a microinverter, device or component with requisite wires connecting it to the rest of the system. The interconnecting wiring is cut to length for the specific application or configuration.
The described solar power systems are typically for large solar panels rather than smaller modules, and do not integrate the parallel wiring into the individual modules. Smaller surface areas (for example architectural features such as long narrow linear building fascias, columns or window frames) cannot accommodate these larger format solar panels.
In summary, the key advantages posited for the photovoltaic modular system include a system that:
incorporates the parallel wiring into each individual module,
is in a smaller format that can fit on a variety of surfaces, even ones that are narrow or small,
allows the modules to be directly connected together without the need for additional interconnecting wiring,
has embedded wiring which allows the modules to be arranged in any configuration, with pairs of module connectors on all four sides of the module,
performs the paralleling function on the DC side prior to converting to AC,
incorporates the control electronics for the paralleling function inside each module,
has a higher resolution for isolating sections of the system that are shaded by incorporating a group of smaller modules rather than one large module,
can adjust to fit both smaller surface areas and be extended to longer areas by adding more modules, and
can be directly attached to a smooth surface area without any other separate support structure.